U.S. patent number 4,283,317 [Application Number 06/187,173] was granted by the patent office on 1981-08-11 for wax-free, hot melt adhesive compositions.
This patent grant is currently assigned to E. I. Du Pont de Nemours and Company. Invention is credited to Charles V. Murphy, Robert J. Statz.
United States Patent |
4,283,317 |
Murphy , et al. |
August 11, 1981 |
Wax-free, hot melt adhesive compositions
Abstract
Wax-free hot melt adhesive compositions based on a copolymer of
an .alpha.-olefin, especially ethylene, with an unsaturated
carboxylic acid, especially an .alpha.,.beta.-unsaturated
carboxylic acid, or with maleic anhydride and optionally also with
another unsaturated carboxylic acid or ester; a tall oil rosin; and
a hydrocarbon oil provide good quality bonds. When the level of oil
is less than 15%, particularly up to about 13%, there is no oil
exudation. The hot melt adhesive compositions of this invention
have a good melt viscosity stability when an antioxidant,
especially a hindered phenol or organic phosphite, is added. These
compositions are useful for heat sealing cartons and for similar
applications. Formulations containing tall oil rosins and
processing oils approved by the Food and Drug Administration can be
readily prepared.
Inventors: |
Murphy; Charles V. (Wilmington,
DE), Statz; Robert J. (Kennett Square, PA) |
Assignee: |
E. I. Du Pont de Nemours and
Company (Wilmington, DE)
|
Family
ID: |
22687886 |
Appl.
No.: |
06/187,173 |
Filed: |
September 15, 1980 |
Current U.S.
Class: |
524/272; 156/327;
156/334 |
Current CPC
Class: |
C09J
123/08 (20130101); C09J 193/04 (20130101); C08L
93/04 (20130101); C08L 23/08 (20130101); C09J
193/04 (20130101); C09J 123/08 (20130101); C08L
2666/04 (20130101); C08L 2666/02 (20130101); C08L
2666/04 (20130101); C08L 2666/02 (20130101) |
Current International
Class: |
C09J
123/08 (20060101); C09J 123/00 (20060101); C09J
193/04 (20060101); C09J 193/00 (20060101); C08L
093/04 (); C08K 005/13 (); C08K 005/52 () |
Field of
Search: |
;260/27R
;156/327,334 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Cockeram; H. S.
Claims
We claim:
1. A wax-free adhesive composition having an initial 177.degree. C.
melt viscosity of about 1000-4000 kPa.multidot.s and consisting
essentially of the following components:
(1) about 20-50 parts of a copolymer of a C.sub.2 -C.sub.10
.alpha.-olefin with an aliphatic, ethylenically unsaturated
carboxylic acid or with maleic anhydride, which copolymer may also
contain another ethylenically unsaturated comonomer selected from
the group consisting of carboxylic acids and carboxylic acid
esters;
(2) about 30-60 parts of a tall oil rosin; and
(3) about 1-13 parts of a hydrocarbon oil; all the above parts
being by weight, and their sum being 100; said adhesive composition
also containing a minor amount of an antioxidant capable of
stabilizing it against viscosity deterioration and substantial
discoloration on heating.
2. A composition of claim 1 wherein the amount of Component (1) is
about 30-50 parts; the amount of Component (2) is about 40-60
parts; and the amount of Component (3) is about 3-7 parts.
3. A composition of claim 2 wherein the tall oil rosin is heat
treated tall oil rosin.
4. A composition of claim 1 wherein the .alpha.-olefin content of
Component (1) is 80-99 weight percent.
5. A composition of claim 4 wherein the .alpha.-olefin content of
Component (1) is 85-95 weight percent.
6. A composition of claim 5 wherein the .alpha.-olefin content of
Component (1) is 90-95 weight percent.
7. A compositin of claim 4 wherein the .alpha.-olefin is
ethylene.
8. A composition of claim 7 wherein Component (1) is a copolymer of
ethylene with an .alpha.,.beta.-unsaturated carboxylic acid.
9. A composition of claim 8 wherein the .alpha.,.beta.-unsaturated
carboxylic acid is represented by the formula ##STR2## where X is
H.sub.1, COOH, or COOR, R being a hydrocarbon radical; and Y is H
or CH.sub.3.
10. A composition of claim 9 wherein the .alpha.,.beta.-unsaturated
carboxylic acid is methacrylic acid.
11. A composition of claim 4 wherein the .alpha.-olefin is ethylene
plus at least one other .alpha.-olefin, the total proportion of the
other .alpha.-olefins being at most about 20 weight percent of the
total .alpha.-olefin content of the copolymer.
12. A composition of claim 1 wherein the amount of antioxidant is
less than 1% of the combined weight of Components (1), (2), and
(3).
13. A composition of claim 12 wherein the antioxidant is selected
from hindered phenols, organic phosphites, and mixtures thereof.
Description
BACKGROUND OF THE INVENTION
This invention is directed to low cost, wax-free, hot melt adhesive
compositions particularly suitable for such applications as, for
example, sealing packaging cartons.
The usual commercial hot melt adhesives are based on a solid,
polymeric thermoplastic material, which is compounded with one or
more tackifiers and waxes and contains additives such as
antioxidants or other stabilizers. The most commonly used
tackifiers are hydrocarbon resins, terpenes, terpene/phenolics,
coumarone/indene resins, polymerized .alpha.- and .beta.-pinenes,
rosin-modified phenolic resins, polymerized rosin, rosin
derivatives such as hydrogenated and dimerized rosins, and tall oil
rosins. Because of their higher heat sensitivity, tall oil rosins
are not normally recommended for use in high quality hot melt
adhesive compositions. Wax, which is a low-melting hydrocarbon
material, serves as a softening point depressant and the same time
as a low cost filler. The usual waxes employed in hot melt adhesive
compositions include paraffin waxes, microcrystalline waxes, and
synthetic waxes. A hot melt adhesive composition naturally must be
heat stable. Decomposition of any component on heating or exudation
at any temperature would make such a composition useless.
Similarly, crystallization of the adhesive on cooling would be very
undesirable. While many high performance, high cost hot melt
adhesives are commercially available, it has been difficult to
formulate a low cost hot melt adhesive composition capable of
providing high strength bonds. For example, a low cost adhesive
might use cheap processing oils instead of expensive waxes, but
oils have not met with good acceptance because of their tendency to
exude.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a wax-free
adhesive composition having an initial 350.degree. F. (177.degree.
C.) melt viscosity of about 1000-4000 kPa.multidot.s and consisting
essentially of the following components:
(1) about 20-50 parts of a copolymer of a C.sub.2 -C.sub.10
.alpha.-olefin with an aliphatic, ethylenically unsaturated
carboxylic acid or with maleic anhydride, which copolymer may also
contain another ethylenically unsaturated comonomer selected from
the group consisting of carboxylic acids and carboxylic acid
esters;
(2) about 30-60 parts of a tall oil rosin; and
(3) about 1-13 parts of a hydrocarbon oil;
all the above parts being by weight, and their sum being 100; said
adhesive composition also containing a minor amount of an
antioxidant capable of stabilizing it against viscosity
deterioration and substantial discoloration on heating.
DETAILED DESCRIPTION OF THE INVENTION
In addition to the low cost requirement, the adhesive compositions
of the present invention must possess acceptable physical
properties. Beside the required melt viscosity range recited in the
Summary of the Invention, satisfactory hot melt adhesive
compositions should have an acceptable softening point, good
tensile strength and elastic modulus, sufficient elongation, and
good adhesive properties.
The desirable properties of such compositions are as follows:
______________________________________ Softening point about 93
.+-. 9.degree. C. Tensile strength 2400-5500 kPa Elongation minimum
60% Elastic modulus minimum 34.5 MPa Lap shear adhesion fail
temperature minimum 71.degree. C. T-Peel at -28.9.degree. C. no
adhesive failure Cold creep more than 8 hours to adhesive failure
______________________________________
The principal component of the hot melt adhesives of the present
invention is the base copolymer, Component (1). The .alpha.-olefin
normally will be ethylene, although other .alpha.-olefins or
mixtures of ethylene with other .alpha.-olefins may be used.
Normally the proportion of the other olefin in the monomer mixture
will be less than the proportion of ethylene, in practice no more
than about 20% of the total .alpha.-olefin makeup. The preferred
.alpha.-olefin other than ethylene is propylene. Other suitable
olefins include, for example, 1-butene, 1-hexene, 1-octene, and
1-decene. Suitable ethylenically unsaturated carboxylic acids may
be either .alpha.,.beta.-unsaturated or unsaturated at a position
farther removed from the carboxylic group, especially in a terminal
position. Suitable .alpha.,.beta.-unsaturated carboxylic acids
include itaconic acid and acids having the following formula
##STR1## where X is H, COOH, or COOR, R being a hydrocarbon
radical; and Y is H or CH.sub.3.
Other types of unsaturated carboxylic acids include, for example,
3,4-butenoic acid, 7,8-heptenoic acid, and undecylenic acid.
Unsaturated carboxylic acids can be copolymerized with
.alpha.-olefins in a well-known manner in the presence of free
radical generators, as described, for example, in U.S. Pat. No.
3,264,272 to Rees, which is herein incorporated by reference.
Maleic anhydride can be grafted on .alpha.-olefin polymers and
copolymers in a free radical-initiated reaction, as also explained
in the above patent, or may be grafted without any free radical
generators on .alpha.-olefin polymers having residual unsaturation
(for example, EPDM copolymers), as described in U.S. Pat. No.
3,884,882 to Caywood. Contrary to the teachings of U.S. Pat. No.
3,264,272, the acid groups should not be for the purpose of this
invention converted to the ionic form. Copolymers of an
.alpha.-olefin with an unsaturated comonomer and carboxylic acid
can be made, for example, as taught in U.S. Pat. No. 3,201,374 to
Simms. In addition to copolymers of .alpha.-olefin with an
unsaturated ester and a carboxylic acid, such copolymers may be
copolymers of an .alpha.-olefin with two different carboxylic
acids, especially .alpha.,.beta.-unsaturated carboxylic acids. The
unsaturated ester may be either a vinyl ester of a saturated
carboxylic acid or an ester of a saturated alcohol and an
unsaturated carboxylic acid. Representative of the former group are
vinyl acetate, vinyl propionate, and vinyl isobutyrate; while those
esters representative of the latter group are methyl acrylate,
methyl methacrylate, dimethyl maleate, monoethyl fumarate, and
mono- or diethyl itaconate.
The preferred proportion of .alpha.-olefin in the copolymers used
in the present adhesive compositions is 80-99% by weight,
preferably 85-95%, and particularly 90-95%. When these proportions
are maintained, the adhesive compositions have good rheological and
adhesive properties.
The preferred adhesive compositions contain about 30-50 parts of
the base polymer, 45-60 parts of tall oil rosin, and 3-7 parts of
hydrocarbon oil. At a level of about 15 parts some oil exudation is
observed at ambient temperature. Hydrocarbon oils suitable in the
instant adhesive compositions are the usual processing oils which
are commercially available from a number of suppliers, for example
Sun Petroleum Products Co., Exxon Corporation, and Shell Chemical
Co. The oils may or may not contain aromatic hydrocarbons in
addition to predominant aliphatic and naphthenic hydrocarbons.
The tall oil rosins used in the adhesive compositions of the
present invention are inexpensive rosins obtained as a by-product
from black liquor soap in paper manufacturing. Tall oil rosins
consist mainly of rosin acids (about 88-92%) plus 4-6% of rosin
esters and anhydrides, 2-5% of unsaponifiable matter, and 1-3% of
fatty acids. A typical rosin acid composition of one commercial
unmodified tall oil rosin is as follows:
______________________________________ Abietic acid 34%
Dehydroabietic acid 24% Palestric acid 9% Dihydroabietic acid 5%
Neoabietic acid 3% Isopimaric acid 6% Pimaric acid 5%
______________________________________
the remainder being unsaponifiable matter and fatty acids.
For the purpose of this invention, it is preferred to use modified
tall oil rosins. Typical treatment methods which reduce the rosin's
tendency to crystallize are: heat treatment, partial neutralization
with sodium hydroxide, and polymerization. The oxidation resistance
of these rosins can be improved by disproportionation,
hydrogenation, maleation, and, to a lesser extent, polymerization.
Heat treatment, which causes disproportionation of abietic acid
into dehydroabietic acid and tetrahydroabietic acid, results in
significant stabilization. Heat treated tall oil rosin is the
preferred tackifying resin in the compositions of the present
invention. While other methods of stabilizing tall oil rosins may
provide equal results, those other methods are more expensive and
would unnecessarily increase the cost of the adhesive
composition.
The adhesive compositions of the present invention should be
stabilized against undesirable viscosity changes and discoloration
under heat conditions. The viscosity normally increases on
prolonged heating, and the industry prefers melt adhesive
compositions which can withstand a 177.degree. C. temperature for
100 hours without a viscosity change of more than about 20%. It is,
however, recognized that the normal case sealing or similar bonding
operations are carried out with adhesive tanks of limited capacity,
which are emptied in the course of at most a few hours of work.
Accordingly, such stringent stability standards may not always be
necessary, and many compositions which have a satisfactory initial
stability would be quite satisfactory for a majority of sealing
operations. While dark color is not necessarily indicative of
decomposition or poor quality, many hot melt adhesive users tend to
associate dark color with degradation and find dark adhesive melts
to be undesirable. Although many commercial antioxidants are used
as stabilizers for a variety of polymeric materials, including
hindered phenols, amines, and organophosphorus compounds, amines
are not considered desirable in the compositions of the present
invention because of their tendency to develop dark color on
heating. Organophosphorus compounds by themselves are more
efficient than hindered phenols by themselves, but one of the best
antioxidant combinations seems to be a mixture of equal weights of
two commercial antioxidants: Irganox.RTM. 1010 (Ciba-Geigy Corp.)
and Weston.RTM. 618 (Borg-Warner Co.). The former is a hindered
phenol--tetrakis[methylene 3-(3'-di-tert-butyl-4'-hydroxyphenyl)
propionate] methane--while the latter is an organic phosphite
ester--di(octadecylpentaerithritol) diphosphite. Another
particularly effective antioxidant is Weston.RTM. TNPP,
tris(nonlyphenyl) phosphite. A properly stabilized adhesive
composition of this invention is light yellow and becomes dark
yellow on heating to its melting temperature. The amount of
antioxidant is less than 1% of the weight of the other components
and may be as little as 0.1% or less. The hot melt adhesive
compositions of the present invention provide good bonding of a
variety of surfaces, for example, paper, cardboard, natural and
synthetic fibers, plastics and elastomers, metals, and wood.
This invention is now illustrated by the following examples of
certain preferred embodiments thereof, where all parts,
proportions, and percentages are by weight, unless otherwise
indicated.
Testing was done as described below.
Oil exudation was observed visually at ambient temperature.
Melt viscosity was measured using a Brookfield RVT Viscometer the
thermocel system complete with Model 63A controller using a No.
SC4-27 spindle.
Melt viscosity stability was determined by obtaining an initial
viscosity reading at 177.degree. C. and then maintaining the
adhesive at 177.degree. C. in a controlled forced air oven for 100
hours. Viscosity was then measured at 177.degree. C. using the
above Brookfield RVT Viscometer and thermocel system.
Softening point was determined by ring and ball apparatus, ASTM
Designation D36-70.
Tensile strength, elongation and modulus of elasticity were
obtained according to ANSI/ASTM D-638-77a.
Adhesive Application Procedures
(a) The test adhesive was applied as a coating to "60-80 lb" kraft
paper with a 15 cm laboratory hot melt coater. The coated paper was
heat-sealed, coated side to coated side using a Sentinel heat
sealer model 12ASL at designated temperatures, pressures and dwell
times. The bond can be either a lap shear or a T-peel type.
(b) A hot melt adhesive gun (Hot Shot Gun, Model No. 200HS,
Adhesive Machinery Corporation) was used to apply an approximate 3
mm adhesive bead to a boxboard substrate. The adhesive bead is
applied at 177.degree. C. and immediately covered with an
equivalent sized piece of boxboard using light hand pressure.
Lap Shear Adhesion Tests--High Temperature
(a) Programmed oven--a lap-shear specimen 2.5 cm in width is
attached to a clamp inside a forced air oven. A 454 g weight is
attached via a clamp to the bottom of the specimen. The oven is
programmed to increase in temperature at a rate of 10.degree.
C./hour. The timer is started and when the specimen bond is
completely broken, the weight falls and trips (stops) the timer.
The fail temperature is calculated based on the initial oven
temperature at the start of the test plus the time/temperature
increase till bond failure.
(b) 24-hour test at designated temperature--a lap shear test
specimen is tested in the same manner as in the programmed oven
test with a 454 g weight attached. The oven is kept at a constant
temperature for a 24 hour period. If the bond does not fail after
24 hours, the temperature is raised 5.55.degree. C. and a new
specimen is tested for 24 hours.
T-peel Adhesion Test--Low Temperature (-28.9.degree. C. or
-32.degree. C.)
A T-peel specimen 2.54 cm in width is placed in a cold box for 24
hours. The test specimen is pulled apart inside the cold box and
observed for type of bond failure (e.g., fiber tear, adhesive
failure, cohesive failure).
Room Temperature Creep Properties
A T-peel specimen 2.54 cm in width is attached to a clamp and a 454
g weight is attached via a clamp to the bottom of the specimen. The
test is conducted under ambient conditions, and the time to
complete bond failure is recorded.
In all cases, the compositions were stabilized by the addition of
0.01%, based on all the components, of
2,6-di-tert-butyl-4-methylphenol.
The results of all the tests were obtained in British units and
then converted to SI units. Temperatures in .degree.F. were
converted to .degree.C.
EXAMPLES 1-8
Examples 1-4 and 6-8 are outside the scope of this invention.
Example 1 is a control example, wherein a commercial, low cost,
melt adhesive containing no oil extender was tested. Examples 7 and
8 provide data for oil-extending compositions based on
ethylene/vinyl acetate (E/VAc) copolymers. Examples 2 and 3 provide
compositions and test results for compositions based on
ethylene/methacrylic acid (E/MAA) copolymers of the type suitable
in this invention but containing higher levels of oil. The
compositions of Examples 4 and 6 have too high melt viscosity.
Finally, Example 5 is entirely within the scope of this invention.
The results are given below in Table I.
TABLE I
__________________________________________________________________________
Composition (%) Example and melt index 1 2 3 4 5 6 7 8
__________________________________________________________________________
Commercial adh. 100 E/MAA (89/11), 100 34 E/MAA (89/11), 100 45 40
E/MAA (89/11), 100 50 40 E/MAA (89/11), 100 40 40 Stabilized tall
oil rosin.sup.1 33 35 40 50 50 50 50 Hydrocarbon oil.sup.2 33 20 10
10 10 10 10 Oil exudation -- Heavy Mod. None None None None None
Viscosity, kPa . s at 121.degree. C. 11100 8700 32600 68000 22900
29900 14600 157500 135.degree. C. 6700 5100 18200 35000 14200 26000
8400 113000 149.degree. C. 4500 3100 10600 19000 7900 15700 5100
70500 163.degree. C. 3100 1900 6300 11100 4700 8900 3300 44000
177.degree. C. 2200 1350 3900 7100 2900 5700 2200 27600 Softening
point .degree.C. ring and ball 99 -- 91 94 91 92 -- -- Tensile
strength, kPa 3866 -- 1323 4123 3040 3861 717 4254 Elongation, % 74
-- 67 560 665 628 606 1103 Peel strength, kPa heat sealed at
121.degree. C..sup.3 14.5 -- 13.1 7.6 15.2 17.2 31.7 -- heat sealed
at 149.degree. C. 11.7 -- 12.4 9.7 16.5 13.8 35.2 --
__________________________________________________________________________
.sup.1 Crosby.RTM. 721, Crosby Chemicals, Inc. .sup.2 Circosol.RTM.
4240, Sun Oil Co. .sup.3 sealed at 138 kPa pressure, dwell time 4
sec. .sup.4 sealed at 138 kPa pressure, dwell time 2 sec.
These examples show that at the level of 10% of hydrocarbon oil
(Examples 4-8), no exudation was observed; that certain
compositions did not have the right melt viscosity at 177.degree.
C. (Examples 4, 6 and 8); and that copolymers of ethylene with
vinyl acetate were not suitable in oil-extended melt adhesive
compositions, either because of high melt viscosity (Example 8) or
because of poor tensile strength (Example 7). The compositions of
Examples 4 and 6, although having correct proportions of all the
components, had an impractically high viscosity. A higher melt
index polymer probably would give good melt adhesive
compositions.
EXAMPLES 9-11
Three different compositions were compared. The results are given
below in Table II. The copolymer was an E/MAA 85/15 copolymer
having a melt index of 101.
TABLE II ______________________________________ Example Composition
% 9 10 11 ______________________________________ Copolymer 40 40 40
Stabilized tall oil rosin.sup.1 50 47.5 45 extending oil.sup.2 10
12.5 15 Oil exudation none none slight Viscosity, kPa . s at
121.degree. C. 32500 25300 24700 135.degree. C. 16200 12800 13100
149.degree. C. 8400 7200 7000 163.degree. C. 5000 4000 4000
177.degree. C. 2700 2300 2200
______________________________________ .sup.1 Crosby.RTM. 721
.sup.2 Circosol.RTM. 4240
It can be seen that all these compositions have good melt
viscosity, but the composition of Example 11 is unsuitable because
of slight oil exudation.
EXAMPLES 12-14
These examples compare the properties of adhesive compositions
based on E/MAA copolymers having different monomer proportions and
melt indices with the control commercial adhesive of Example 1. The
results are given in Table III. The same rosin and oil were used as
in the preceding examples.
TABLE III
__________________________________________________________________________
Viscosity, Soft. Tensile Copolymer kPa . s at Point strength
Elongation, Example Composition % MAA % Melt Index 177.degree. C.
.degree.C. kPa %
__________________________________________________________________________
12 Commercial adhesive -- -- 2400 98.3 5406 47 13
Copolymer/rosin/oil 50/40/10 10 91 6400 95.6 5102 590
Copolymer/rosin/oil 50/40/10 10 140 4600 96.7 3999 460
Copolymer/rosin/oil 50/40/10 10 199 5000 97.8 3999 580
Copolymer/rosin/oil 50/40/10 10 453 1800 97.2 3034 230
Copolymer/rosin/oil 50/40/10 5 107 5800 103.3 3793 410
Copolymer/rosin/oil 50/40/10 5 195 4200 102.2 3930 180
Copolymer/rosin/oil 50/40/10 5 453 2200 101.1 4274 100 14
Copolymer/resin/oil 40/50/10 10 91 3900 93.3 3585 620
Copolymer/resin/oil 40/50/10 10 199 2400 98.9 3103 270
Copolymer/resin/oil 40/50/10 10 453 900 96.7 2275 390
Copolymer/resin/oil 40/50/10 5 107 2900 101.7 3585 350
Copolymer/resin/oil 40/50/10 5 195 2000 102.8 2896 360
Copolymer/resin/oil 40/50/10 5 453 1500 104.4 4137 150
__________________________________________________________________________
The above data show that even for equal monomer makeup, copolymers
having different melt indices will give different results; but it
is possible to predict the direction of change and accordingly
select the proper copolymer in the right proportion to achieve the
desired result.
EXAMPLES 15-21
These examples compare different formulations of melt adhesive
compositions using various types of tall oil rosins and different
extending oils. The copolymer was in all cases an E/MAA 95/5
copolymer having a melt index of 196. The adhesive composition was
in all cases a blend of copolymer/tall oil rosin/hydrocarbon oil in
the respective proportions of 40/50/10. The results are given in
Table IV.
TABLE IV
__________________________________________________________________________
Example 15 16 17 18 19 20 21 Composition Stabilized.sup.1
Stabilized.sup.1 Stabilized.sup.1 Modified.sup.2 Unmodified.sup.3
Unmodified.sup.4 Disproportionated.sup.5 Tall oil rosin
Circosol.RTM. Sunthene.RTM. Flexon.RTM. Sunthene.RTM. Sunthene.RTM.
Sunthene.RTM. Sunthene.RTM. Hydrocarbon oil 4240.sup.6 410.sup.6
765.sup.7 410.sup.6 410.sup.6 410.sup.6 410.sup.6
__________________________________________________________________________
Viscosity, kPa . s at 121.degree. C. 18000 16000 12000 17500 14300
13300 16000 149.degree. C. 5600 5300 3300 4800 5000 4600 6000
177.degree. C. 1850 2200 2000 2000 2050 1900 2500 After 100 hrs at
177.degree. C. 2400 -- 1000 2200 1900 1800 -- Soft. Point, ring
& ball 93.3.degree. C. 100.degree. C. 100.degree. C.
99.4.degree. C. 99.4.degree. C. 99.4.degree. C. 100.degree. C.
Tensile strength, kPa 3999 2937 2827 2758 2330 3151 2160
Elongation, % 540 242 264 174 160 571 193 Shore D hardness 95 92 89
86 86 87 78
__________________________________________________________________________
.sup.1 Crosby.RTM. 721, Crosby Chemicals, Inc. .sup.2 Sylvatac.RTM.
RX, Sylvachem Corporation .sup.3 Acintol.RTM. RS, Arizona Chemical
Co. .sup.4 Acintol.RTM. R3A, Arizona Chemical Co. .sup.5 Nilox.RTM.
STOR588-41-1, Reichhold Chemical Co. .sup.6 Sun Co. .sup.7 Exxon
Corp.
It is of interest to note that all the above tall oil rosins and
two hydrocarbon oils have been approved by the Food and Drug
Administration for use in sealing food-containing cartons.
EXAMPLES 22-27
These examples compare the physical and adhesive properties of
several compositions of this invention. In all cases, the base
copolymer was an ethylene/acrylic acid copolymer. The tall oil was
an unmodified commercial grade, and the hydrocarbon oil was
Flexon.RTM. 760 (Exxon Corp.). The data are tabulated below.
TABLE V
__________________________________________________________________________
Example Composition 22 23 24 25 26 27
__________________________________________________________________________
Copolymer Acryl. Acid, % 10 10 15 5 10 15 Melt Index 120 230 105
300 230 180 Adhesive Comp. Copolymer 40 40 40 42 42 42 Tall Oil
Rosin 55 55 55 53 53 53 Hydrocarbon Oil 5 5 5 5 5 5 Viscosity at
177.degree. C., kPa . s 3250 2300 3400 2000 3000 3700 After 100 hrs
at 177.degree. C. 7700 4800 8800 3000 4000 7000 Tensile strength,
kPa 5116 4420 3799 3206 3551 3489 Elongation, % 475 497 431 380 521
525 Elastic modulus, MPa 103.4 114.5 18.6 77.2 44.8 20 Lap shear
fail temp. .degree.C. (programmed oven) 85 84 69 95 83 63 Run temp.
creep. over over over over time to failure 10 days 2 wks 2 wks 30.5
hrs 2 wks 2 wks 1.25 cm No creep. 1.25 cm No creep. creep. creep.
Low temp. adhesion -32.degree. C. Fiber Fiber Fiber Fiber Fiber
Fiber Tear Tear Tear Tear Tear Tear
__________________________________________________________________________
It can be seen that only the compositions of Examples 25 and 26
maintained their 177.degree. C. viscosities within the 1000-4000
kPa.multidot.s range after a 100 hr heat cycle. However, the
absolute values of these viscosities increased considerably. This
problem, which did not occur with E/MAA copolymers, could, however,
be corrected by substituting for the original antioxidant
(2,6-di-tert-butyl-4-methylphenol) 0.5%, based on the weight of all
the other components, of either tri(nonylphenyl) phosphite or a
mixture of equal amounts of Irganox.RTM. 1010 and Weston.RTM. 618.
When the composition of Example 25 was modified in this manner, the
original 177.degree. C. viscosity changed from 2000 to 2100
kPa.multidot.s in the former case and from 1800 to 2200
kPa.multidot.s in the latter case.
EXAMPLES 28-34
Adhesive compositions based on a copolymer of ethylene with
methacrylic acid were prepared with the same tall oil rosin and
process oil as in Examples 21-26 and compared in the same manner.
The results are shown in Table VI, below. The standard antioxidant,
2,6-di-tert-butyl-4-methylphenol, was used in all compositions.
TABLE VI
__________________________________________________________________________
Example Composition 28 29 30 31 32 33 34
__________________________________________________________________________
Copolymer MAA % 11 11 12 12 5 11.4 11.2 Melt Index 100 100 209 209
197 128 209 Adhesive Comp. Copolymer/ Rosin/Oil 40/53/7 40/54/6
40/55/5 40/55/5 40/55/5 40/55/5 40/55/5 Viscosity at 177.degree.
C., kPa . s 3900 3000 1800 1900 -- 2550 1500 After 100 hrs at
177.degree. C. -- 2440 1950 2050 -- 2775 1525 Adhesion properties
Lap shear fail temp. .degree.C. (programmed oven) 83.degree. C.
83.degree. C. 83.degree. C. 85.degree. C. -- 85.degree. C.
86.degree. C. Low temp. adhesion Fiber Fiber Cohesive Fiber
Cohesive Fiber Fiber 24 hr at -28.9.degree. C. Tear Tear Failure
Tear Failure Tear Tear Room temp. creep over over over over time to
failure 990 25 36 61 57 142 18 Tensile strength, kPa 3048 4358 3551
3482 3110 3558 3192 Elongation, % 700 614 564 577 585 587 607
Elastic modulus, MPa 14.1 28.9 31 26.2 42.3 23.8 10.9 Softening
point, .degree.C. 91.1 92.2 90 90.6 -- 91.7 88.9
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All the above compositions had good adhesive, rheological, and
physical properties.
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